Inhibitory effect of a dendritic epidermal T cell line on K1735 melanoma cells in vivo and in vitro.

Murine epidermis contains a resident population of dendritic epidermal T cells (DETCs) with unknown function. We tested the ability of a cultured line of these cells to inhibit the growth of murine melanoma cells in vitro and in vivo. The interleukin-2 (IL-2)-dependent T cell line AU16, derived from the epidermis of C3H mice, was used as the source of DETCs. AU16 cells were cytotoxic to syngeneic K1735 and CM3205 C3H melanoma cell lines, as well as to a chemically induced cutaneous fibrosarcoma, in an in vitro 51Cr release assay. Mixing viable AU16 cells, but not splenic T cells, with K1735 melanoma cells immediately before intradermal injection into the flank of mice prevented or delayed the outgrowth of melanomas. AU16 cells killed by freezing and thawing and supernatants from cultures of AU16 cells did not inhibit melanoma growth in vivo or in vitro. Injection of viable AU16 cells intravenously or at a separate intradermal site had no effect on melanoma growth. These studies suggest that IL-2-activated DETCs have the potential to inhibit the growth of melanoma cells in vivo and that their cytotoxic activity may be responsible for this effect.